Abstract:

A probe mounted directly to a conduit conveying a process stream of gas to
be analyzed, which can condition a continuous sample of the gas before it
is analyzed by removing undesirable vapor components of the sample
through interaction with a heat exchanger conduit which condenses these
components into a liquid such that they precipitate under the force of
gravity back into the process stream. The probe uses a Venturi device to
motivate the gas through a flow cell chamber where it interacts with
light shown through the chamber before ejecting the sample back into the
process stream through a sample return conduit.

Claims:

1) An in-situ probe for use in a sulfur recovery process comprising:a
probe head manifold comprising a plurality of discs; said discs further
comprising a cylindrical flow cell chamber, a serpentine channel, and a
Venturi device;a sample chamber having one end directly connected to said
probe head manifold and the other end open for immersion in a process
fluid for conveying a continuous stream of said sample of said process
fluid to said flow cell chamber, wherein said sample chamber contains a
plurality of conduits, said conduits further comprising:a heat exchanger
conduit for conveying a cooling fluid that is cooler than said sample
from a first orifice in said probe head manifold, through the interior
volume of said sample chamber, and through a second orifice in said probe
head manifold;a sample return conduit directly connected to a third
orifice in said probe head manifold, said third orifice being connected
to said Venturi device for conveying said sample from said flow cell
chamber to be ejected back into said process fluid.

2) The probe of claim 1 wherein said discs are aligned concentrically.

3) The probe of claim 2 wherein said sample chamber is aligned
concentrically with said discs.

4) The probe of claim 1 wherein said flow cell chamber comprises an
optical inlet orifice and an optical outlet orifice concentrically
aligned along the longitudinal axis of said flow cell chamber.

5) The probe of claim 4 wherein said flow cell chamber further comprises a
sample inlet orifice and a sample outlet orifice aligned perpendicularly
to the longitudinal axis of said flow cell chamber.

6) The probe of claim 1 wherein said serpentine channel is adjacent to
said flow cell chamber and conveys a heating fluid that is hotter than
said sample.

7) The probe of claim 6 wherein said serpentine channel comprises a
heating fluid inlet orifice and a heating fluid outlet orifice in said
probe head manifold.

8) The probe of claim 7 wherein said heating fluid raises the temperature
of said sample in said flow cell chamber to a point where all components
of said sample remain in a vapor state while inside said flow cell
chamber.

9) The probe of claim 8 wherein said heating fluid is steam.

10) The probe of claim 1 wherein said Venturi device receives an
aspirating fluid through an aspirator inlet connection orifice in said
probe head manifold.

11) The probe of claim 10 wherein said Venturi device comprises a
bottleneck for increasing the velocity of said aspirating fluid.

12) The probe of claim 1 wherein said sample chamber contains a sample
return orifice aligned perpendicularly to the longitudinal axis of said
sample chamber that is directly connected to said sample return conduit.

13) The probe of claim 1 wherein said heat exchanger conduit is aligned
concentrically with the longitudinal axis of said sample chamber.

14) The probe of claim 13 wherein said heat exchanger conduit comprises
two tubes wherein the outer tube is of larger diameter and of greater
length than the inner tube.

15) The probe of claim 14 wherein said outer tube is aligned
concentrically with the longitudinal axis of said sample chamber.

16) The probe of claim 15 wherein said first and second tube each have one
end flush against said Probe head manifold such that one end of each tube
are coplanar.

17) The probe of claim 16 wherein the end of said second tube furthest
from said probe head manifold is capped such that said cooling fluid
cannot escape outside said heat exchanger conduit and said sample cannot
enter said heat exchanger conduit.

18) The probe of claim 17 wherein said cooling fluid enters said inner
tube through said flush end with said probe head manifold, then exits
through the opposite end of said inner tube into the space between said
inner tube and said outer tube and travels opposite the flow in said
inner tube back into said probe head manifold.

19) The probe of claim 18 wherein said cooling fluid lowers the surface
temperature of said heat exchanger conduit to a point above the freezing
temperature and below the boiling temperature of one or more undesirable
components of said sample so they will condense into liquid phase and
precipitate against the flow of said sample under the force of gravity
back into said process fluid as a liquid through said open end of said
sample chamber.

22) The probe of claim 21 wherein the pressure of said steam is controlled
by a pressure regulating means such that the surface temperature of said
heat exchanger conduit can be controlled by adjusting said pressure
regulating means.

23) The probe of claim 22 wherein said pressure regulating means is
adjustable such that the temperature of said steam is above the
condensation point of said sulfur vapor.

24) The probe of claim 23 wherein said pressure regulating means is
adjustable such that the temperature of said steam is below the freezing
point of said sulfur vapor.

25) The probe of claim 24 wherein said flow cell chamber is in optical
communication with a gas analyzer that measures the concentration of said
sulfur vapor in said flow cell chamber.

26) The probe of claim 25 wherein the pressure of said steam is raised or
lowered in response to the concentration of sulfur vapor detected in said
flow cell chamber by said gas analyzer such that the concentration of
sulfur vapor in said flow cell chamber is minimized.

27) The probe of claim 26 wherein the pressure of said steam is raised
periodically such that the heat exchanger conduit heats said sample
significantly higher than the boiling temperature of said sulfur vapor
such that any sulfur vapor that had previously condensed downstream of
said sample chamber is re-vaporized and conveyed through said sample
return conduit and ejected back into said process fluid.

Description:

[0002]This invention relates to a probe for conditioning a fluid sample to
be analyzed having one or more undesirable components entrained therein.
In particular, it relates to a system that can very precisely cool the
sample to remove just the undesirable components through condensation. In
a process gas stream it is often desirable to know the concentration of
one or more compounds that make up the process stream. This concentration
knowledge allows feedback to be sent to an operator(s) or equipment in
the process that can make changes based on the information obtained. For
example, in a Claus sulfur recovery process H2S and SO2 are
reacted to produce elemental sulfur and water. By analyzing the
concentration of H2S leftover in the tail-gas from the reaction,
feedback can be provided that can be used to adjust the amount of
H2S being supplied to the reaction. However, analysis of the
tail-gas is complicated by the presence of elemental sulfur vapor which
distorts the readings obtained from a spectrometer, and which can
solidify on the analyzing equipment's interior surface. Therefore it is
an object of the present invention to provide an in-situ probe that can
remove sulfur vapor from a process gas stream by condensing the vapor
into a liquid such that it precipitates into the process stream before it
can accumulate on the analyzing equipment's interior surface.

SUMMARY OF THE INVENTION

[0003]A sample of a process gas steam, which contains at least one
undesirable component such as sulfur vapor, is conveyed by means of a
Venturi device into a sample chamber where it interacts with a heat
exchanger conduit. The heat exchanger conduit conveys a cooling fluid,
such as steam, through a separate chamber that is not in fluid
communication with the sample chamber as to preclude mixing of the
cooling fluid and sample, but allows for heat transfer from the process
gas steam sample to the cooling fluid through the wall of the heat
exchanger conduit. The temperature of the cooling fluid is precisely
controlled--in the case of steam this is accomplished by regulating the
pressure of the steam--so that the undesirable component of the process
gas steam sample will condense into a liquid. The undesirable component
of the process gas steam sample precipitates out of the sample and falls
under the force of gravity back into the process gas stream. In the case
of sulfur being the undesirable component, it is of paramount importance
that the temperature of the cooling fluid be very precisely controlled,
because the pressure in a Claus process tail-gas line is kept below
atmospheric pressure to prevent the possibility of gas leaking from the
pipes, and at this sub-atmospheric pressure sulfur only exists in a
liquid state within a very narrow temperature range. The reason pressure
control is important is because if the temperature of the cooling fluid
were to be too low, sulfur vapor will solidify on the surface of the heat
exchanger conduit and insulate it such that the process gas steam sample
will be able to pass by without its sulfur vapor content being removed,
conversely, if the temperature of the cooling fluid is too high sulfur
vapor will not condense leading to the same problem. Therefore, it is a
critical aspect of this invention that the system can be adjusted such
that sulfur can be condensed to a liquid through interaction with the
heat exchanger conduit. After interaction with the heat exchanger conduit
the process gas steam sample travels through an orifice in the bottom of
a probe head manifold and into a flow cell chamber. The flow cell chamber
is cylindrical with an inlet and outlet orifice for the process gas steam
sample to enter and exit the flow cell chamber which is aligned
perpendicular to the longitudinal axis of the sample chamber, and an
optical inlet and outlet orifice with one in each and of the flow cell
chamber aligned parallel and concentrically with and the longitudinal
axis of the flow cell chamber such that a beam of light can be shown
through the flow cell chamber entering through the optical inlet orifice
and exiting through the optical outlet orifice. In this way some
wavelengths of light being shown through the chamber will be absorbed by
the sample in accordance with Beer-Lamberts law, and the light exiting
the chamber can be analyzed by a spectrometer to identify the components
of the process gas steam sample in the flow cell chamber.

[0004]The flow cell chamber is also in close proximity to a demister which
conveys a heating fluid, such as steam, through a serpentine channel. The
serpentine channel is positioned in such a way that it is not in fluid
communication with the flow cell chamber, which precludes mixing of the
heating fluid and the process gas steam sample, but allows for heat
transfer from the heating fluid to the process gas steam sample through
the wall of the flow cell chamber. The demister further comprises a
heating fluid inlet and outlet orifice to allow the heating fluid to
enter the serpentine channel through one end and exit through the
opposite end. This heating fluid system allows the temperature of the
flow cell chamber to be held at a point above the condensation
temperature of all components of the process gas steam sample so that
liquids and solids do not accumulate in the chamber and block the flow of
the process gas steam sample and light through the chamber.

[0005]After the process gas steam sample exits the flow cell chamber it
passes through the Venturi device where it mixes with an aspirating
fluid, such as air, and is conveyed through a sample return conduit,
which is housed in the sample chamber but not in fluid communication
therewith, before being ejected back into the original process fluid
downstream of the inlet of the sample chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 depicts the preferred embodiment of the present invention.

[0008]In reference to the drawing, it is to be understood that the
depiction therein is for illustration of a preferred embodiment of the
invention, and the invention is not limited thereto.

[0009]As shown in FIG. 1, an in-situ gas analyzer probe 1 is mounted to a
process pipe 2 carrying tail-gas 3 in a conventional Claus sulfur
recovery operation (represented by box 99). The tail-gas is made up of
multiple components including H2S, S2, and H2O, and is
held at a pressure below atmospheric pressure and a temperature where all
components exist in a vapor form. The tail-gas passes by the bottom end
of a sample chamber 4 which extends, preferably approximately 2/3 of the
way, into the process pipe 2. The bottom end of sample chamber 4 is cut
at an angle of approximately 45 degrees to the longitudinal axis of the
process pipe 2 and oriented to form an opening 98 that faces the oncoming
flow. The opening 98 is cut at an angle in order to increase the
opening's area that is perpendicular to the flow in the process pipe 2 to
facilitate the flow of a sample 5 of the tail-gas 3 into sample chamber
4.

[0010]The tail-gas sample 5 is motivated through the sample chamber 4, a
flow cell chamber 6, and a sample return conduit 7 by a Venturi device 8.
Referring now to FIG. 2, the Venturi device 8 comprises an aspirating
fluid inlet orifice 9, a sample inlet orifice 10, and a common outlet
orifice 11. The Venturi device 8 operates by flowing an aspirating fluid
12, such as air, into the aspirating fluid inlet orifice 9 where it is
conveyed through a bottleneck constriction area 13. The bottleneck
constriction area increases the velocity of the aspirating fluid 12 and
consequently lowers the pressure within the bottleneck constriction 13 in
accordance with Bernoulli's principal. The sample inlet orifice 10 is
located near, but preferably at, the midpoint of the bottleneck
constriction area 13, such that when sized properly the pressure in the
bottleneck constriction area 13 is lower than that of the tail-gas sample
5 upstream of the sample inlet orifice 10. That pressure differential
causes the tail-gas sample 5 to flow through the sample inlet orifice 10
into the bottleneck constriction area 13 wherein the tail-gas sample 5
mixes with the aspirating fluid 12 and exits the Venturi device 8 through
the common outlet orifice 11.

[0011]Reverting to FIG. 1, the sample chamber 4 houses a heat exchanger
conduit 14. Heat exchanger conduit 14 is comprised of an inner tube 15
and an outer tube 16 of different diameters such that the inner tube 15
fits inside the outer tube 16, and of different lengths such that the
inner tube 15 is shorter than the outer tube 16. Both the inner tube 15
and the outer tube 16 are aligned such that one end of each is coplanar
with the end of the sample chamber 4 opposite the end through which the
tail-gas sample 5 is entering, and the coplanar end of the inner tube 15,
outer tube 16, and sample chamber 4 are flush against the flat bottom
side of a probe head manifold 17.

[0012]The circumference of inner tube 15 on the coplanar end encircles a
cooling fluid inlet orifice 18 in the bottom of the probe head manifold
17; such that a cooling fluid 19, such as and not limited to steam, can
be conveyed from a cooling fluid source 97. The cooling fluid source 97
provides the cooling fluid 19 into the probe head manifold 17 through a
connection inlet orifice 20, the inlet orifice then directs the cooling
fluid 19 through the interior volume of the inner tube 15. The cooling
fluid 19 can then pass out of the bottom end of the inner tube 15
opposite the coplanar end, and enter the space encapsulated by the outer
tube's 16 inside diameter and the inner tube's 15 outside diameter. The
cooling fluid 19 then passes through a cooling fluid outlet orifice 21 in
the bottom of the probe head manifold 17 that is encircled within the
outer tube's 16 circumference but not the inner tube's 15 circumference.
The cooling fluid 19 exits the probe head manifold 17 through a cooling
fluid connection outlet orifice 22. The end of the outer tube 16 opposite
the coplanar end is, obviously, sealed so as to preclude the mixing of
the cooling fluid 19 with the tail-gas sample 5 in the sample chamber 4,
and allows for heat transfer between the tail-gas sample 5 and the
cooling fluid 19 through the wall of the heat exchanger conduit 14, in
particular the outer tube's 16 walls.

[0013]The tail-gas sample 5 in the sample chamber 4 flows past the heat
exchanger conduit 14 where thermal energy is exchanged between the
tail-gas sample 5 and the cooling fluid 19. In normal operation the
temperature of the cooling fluid 19 is kept below the tail-gas sample's 5
temperature so that heat is transferred from the tail-gas sample 5 to the
cooling fluid 19. In the preferred embodiment of the present invention
the cooling fluid 19 is steam in which case the temperature of the
cooling fluid 19 can be adjusted by regulating the pressure of the steam
within a conventional pressure regulator 96.

[0014]The pressure of the cooling fluid 19 (preferably steam) must be
precisely controlled such that the temperature of the steam will cool the
tail-gas sample 5 to a point where the S2 component will condense
into a liquid, and not to a point that it will freeze into a solid. The
liquid sulfur 23 then precipitates under the force of gravity against the
flow of tail-gas sample 5 and passes back through the bottom end of a
sample chamber 4 and into the process pipe 2, as illustrated in FIG. 1.

[0015]The tail-gas sample 5 exits the sample chamber 4 though a sample
supply orifice 24 in the bottom side of the probe head manifold 17, and
flows through a sample inlet orifice 25 into flow cell chamber 6.

[0016]The flow cell chamber 6 is cylindrical with an optical inlet orifice
26 on one end of the flow cell chamber 6 and an optical outlet orifice 27
on the opposite end. Both optical inlet orifice 26 and optical outlet
orifice 27 are aligned parallel to, and concentrically upon, the
longitudinal axis of the flow cell chamber such that a beam of light
(depicted by broken arrows) can be shown through the flow cell chamber 6.
Optical inlet orifice 26 and optical outlet orifice 27 each contain a
lens 28 which allows the light to pass through the flow cell chamber 6,
but precludes the tail-gas sample 5 from escaping.

[0017]The light is generated by a conventional light source 90, that
radiates specific wavelengths, or specific ranges of wavelengths that are
required to properly analyze components and concentration of components
in the tail-gas sample. In this way some wavelengths of light being shown
through the flow cell chamber 6 will be absorbed by the sample in
accordance with Beer-Lamberts law. The light exiting the flow cell
chamber 6 can be analyzed by a conventional spectrometer 92 to identify
the components of the process gas steam sample in the flow cell chamber
6.

[0018]Flow cell chamber 6 is in close proximity to a demister 29. The
demister 29 comprises a heating fluid inlet orifice 30, a heating fluid
outlet orifice 31, and a serpentine channel 32. A heating fluid, such as
steam, from a heating fluid source 95, enters the serpentine channel 32
through the heating fluid inlet orifice 30 and is conveyed through the
convoluted path of the serpentine channel 32 above the flow cell chamber
6. The heating fluid then exits through the heating fluid outlet orifice
31. The heating fluid is hotter than the vaporization temperature of each
component of the tail-gas sample 5 in the flow cell chamber 6 and keeps
the tail-gas sample entirely in vapor form such that condensation will
not form on the lenses 28 and solid particulates will not form and impede
the flow of tail-gas sample 5 through the system.

[0019]The tail-gas sample 5 exits flow cell chamber 6 through a sample
outlet orifice 34 and passes through the Venturi device 8. After passing
through the Venturi device 8--which is described in detail above--, the
tail-gas sample is then conveyed through sample return conduit 7 before
being ejected back into the process pipe 2 through sample ejection
orifice 36.

[0020]The probe head manifold 17 is comprised of three concentric discs of
approximately the same diameter. The probe head manifold 17 is split into
discs for manufacturability, maintainability, and to allow each part to
be replaced without having to replace the entire probe head manifold.
Despite this objective of the instant invention, those skilled in the art
will recognize the probe head manifold can be made from one solid piece,
or further divided into more than three discs depending upon the
particular application in which it is used.

[0021]The bottom most disc 37 is directly connected to the coplanar ends
of the inner tube 15 and outer tube 16 of the heat exchanger conduit 14
as well as the sample chamber 4, and comprises the cooling fluid
connection inlet orifice 20, the cooling fluid connection outlet orifice
22, the cooling fluid inlet orifice 18, and the cooling fluid outlet
orifice 21.

[0022]The middle disc 38 is directly connected to the top of the bottom
most disc 37, and comprises the Venturi device 8 as well as an aspirating
fluid connection inlet orifice 39. The aspirating fluid connection inlet
orifice 39 is interconnected to an aspirating fluid source 88. The
aspirating fluid source 88 provides the aspirating fluid 12, such as air,
and pushes the aspirating fluid 12 into the aspirating fluid inlet
orifice 9 as described above.

[0023]The top most disc 40 is directly connected to the top of the middle
disc 38 and comprises the flow cell chamber 6 as well as the demister 29.

[0024]Over time a small amount of S2 vapor will make it past the heat
exchanger conduit 14 and freeze into a solid form elsewhere in the
system. Therefore it is desirable to periodically raise the temperature
of the cooling fluid 19 higher than the vaporization temperature of
S2. By occasionally raising the cooling fluid's temperature in the
fluid inlet orifice 20, the heated cooling fluid temporarily heats the
tail-gas sample 5 so that as the tail-gas sample 5 passes through the
rest of the system it vaporizes any accumulated S2, and in doing so
effectively cleans the system without having to remove and disassemble
the probe.

[0025]Although the present invention has been described and illustrated
with reference to specific illustrative embodiments thereof, it is not
intended the invention be limited to those illustrative embodiments.
Those skilled in the art will recognize that variations and modifications
can be made without departing from the spirit and scope of the claimed
invention.